Location: Crop Genetics Research
2018 Annual Report
Objectives
Objective 1. Characterize new sources of reniform nematode resistance in Gossypium (G.) arboreum and G. herbaceum germplasm accessions and identify DNA markers associated with resistance.
Objective 2. Introgress reniform nematode resistance from G. arboreum and G.
herbaceum accessions into G. hirsutum and develop breeding lines with resistance.
Objective 3. Determine effectiveness of unique sources of reniform resistance fromdiploid Gossypium germplasm accessions on nematode growth, reproduction, and
infection.
Objective 4. Characterize plant growth and development and yield responses to reniform nematode in susceptible and resistant cotton lines and define the relationships between soil fertility and reniform nematode severity with respect to plant damage and yield loss.
Subobjective 4a. Characterize plant growth and development and yield responses to reniform nematode in susceptible and resistant cotton lines.
Subobjective 4b. Define the relationships between soil fertility and reniform nematode severity with respect to plant damage and yield loss in susceptible and resistant cotton lines.
Objective 5. Evaluate impacts of integrated reniform nematode management practices on cotton yield, quality and reniform nematode population densities.
Subobjective 5a. Investigate the efficacy of new commercially-available nematicides on the management of the reniform nematode, cotton yield and cotton fiber quality.
Subobjective 5b. Investigate the effect of rotation with non-host/poor-host crops on management of the reniform nematode and crop yield.
Approach
Develop populations by crossing resistant accessions with one or more Gossypium (G.) arboreum accessions classified as susceptible or highly susceptible. Ovule culture will be used for the introgression of resistance from G. arboreum and G. herbaceum accessions to G. hirsutum varieties. Gossypium accessions with high levels of resistance to reniform nematode will be evaluated in growth chamber experiments to measure the effects of the resistance on number of infections, rate of development of females after infection, and production of eggs. Classical growth and agronomic analysis will be conducted over two years under field conditions at Mississippi State University’s Delta Research and Extension Center in Stoneville, Mississippi. A nutrient response experiment will be conducted under controlled environmental conditions. The relative efficacy of new seed-applied and in-furrow nematicides against the reniform nematode will be evaluated on one susceptible and two resistant cotton lines in a field trial to be established in two naturally-infested sites in Stoneville, Mississippi. A field trial will be established in a reniform nematode infested site in Stoneville, Mississippi.
Progress Report
This research is designed to improve our understanding of the effects of reniform nematode on yield losses in upland cotton (Gossypium hirsutum) and to develop management strategies that will reduce those losses.
We successfully created a large number of populations to help us determine how resistance to reniform nematode is genetically controlled, and to help us identify DNA markers associated with that resistance. Twenty-six Asiatic cotton varieties from the Gossypium arboreum germplasm collection showing high levels of resistance to reniform nematode were crossed with highly susceptible varieties from this collection. Seeds from these crosses have been planted in the field to produce populations that will segregate for reniform nematode resistance in order to evaluate the genetics of resistance. DNA sequence data have been obtained from these varieties and the identification of DNA markers associated with resistance is underway. After these resistance genes are transferred to cotton, breeders can use the markers we identify to rapidly select the materials that are likely to show resistance to reniform nematode. Resistance from these Asiatic cotton varieties is being transferred to upland cotton. The transfer process is difficult and requires special techniques for extracting the developing hybrid cotton embryos, growing them on artificial media, and regenerating plants. One hybrid plant was successfully recovered for the Gossypium arboreum variety PI 615755.
Plants that are considered resistant to reniform nematode will reduce the population of the nematode over time. However, not all resistant cotton varieties will achieve this reduction in the same manner. Experiments were initiated to determine what mechanisms our most resistant plants use to suppress nematode populations, which might include limiting the number of nematodes that can infect the plant roots, stopping growth and development of the nematodes after they infect the roots, or limiting reproduction by the nematodes. During this project cycle, we investigated these mechanisms in multiple experiments for two Gossypium arboreum varieties (A2-190 and A2-100) that we identified as being very resistant to reniform nematode. Experiments were completed on schedule and data analysis is in progress.
A field trial designed to characterize plant growth and development and yield responses to reniform nematode in susceptible and resistant cotton varieties was successfully completed during the 2017 field season. The plants were tested in a field that was infested with reniform nematode. The results of the trial showed that, as soon as 30 days after planting, the resistant varieties 08SS110-NE06 and 08SS100 had significantly greater transpiration, photosynthesis, stomatal conductance, and carbon dioxide assimilation efficiency than the susceptible varieties Deltapine 16 and PHY 490 W3FE. These differences in physiological functions of the plants translated to differences in the rate of plant growth and development. For example, time to reach a first true leaf and time to set the first flower buds were delayed by one week in PHY 490 W3FE compared to resistant varieties. Moreover, resistant varieties were taller and had more nodes, leaf area, and fruits than susceptible varieties throughout the season. Greater vigor in the resistant varieties might have significantly lowered the degree of damage caused by reniform nematodes, and contributed to a 33% yield increase over susceptible varieties. Reniform nematode reproduction was significantly suppressed at the end of the season in plots grown with the resistant varieties compared to susceptible varieties. This test is being repeated in 2018. Early trends appear similar to 2017, where resistant varieties are larger and have higher photosynthetic rates, when compared to susceptible varieties.
Cotton growth and development can be influenced by availability of plant nutrients, so another aspect of this research seeks to define the relationships between soil fertility and reniform nematode severity with respect to plant damage and yield loss in susceptible and resistant cotton varieties. Seed of resistant varieties for studies planned under this subobjective was increased the 2017 growing season. Growth chambers were purchased and installed for use the experiments, and the irrigation and potting system have been manufactured. We are currently testing the system and anticipate trials to begin in August 2018.
To determine how to best manage the use of new cotton varieties with resistance to reniform nematode in a production environment, their use is being evaluated in conjunction with commercial seed-treatment nematicides and crop rotation. Seeds of the resistant variety M123-1337 for use in these studies were obtained and planted in the field for increase during the 2017 season to generate a sufficient amount of seed to conduct the planned experiments. There were sufficient amounts of seed to plant only one field study in 2017; because it is a multi-year test, the rotation study was planted. Seed treatment field trials were delayed until the second year of the project.
The first year of a five-year rotational study was completed during the 2017 season. Peanut and corn were the two main rotational crops planted, with a block of continuous cotton for the purpose of comparison over time. Both peanut and corn reduced nematode numbers during the cropping season, whereas nematode populations increased on cotton. At harvest, the maximum numbers of reniform nematodes per kilogram of soil were reduced from 13,444 to 4,245 for peanut and from 4,953 to 2,832 for corn, but on cotton the numbers increased from 7,706 to 13,444. Yield data were collected and analysis is in progress. Plots for the second year of the study were established on schedule in 2018, and early-season sampling has been completed.
Accomplishments
Review Publications
Erpelding, J.E., Stetina, S.R. 2018. Genetic characterization of reniform nematode resistance for Gossypium arboreum accession PI 417895. Plant Breeding. 137:81-88. https://doi.org/10.1111/pbr.12560.
Zeng, L., Stetina, S.R., Erpelding, J.E., Bechere, E., Turley, R.B., Scheffler, J.A. 2018. History and current research in the USDA-ARS cotton breeding program at Stoneville, MS. Journal of Cotton Science. 22:24-35.
Khanal, C., McGawley, E.C., Overstreet, C., Stetina, S.R. 2018. The elusive search for reniform nematode resistance in cotton. Phytopathology. 108:532-541. https://doi.org/10.1094/PHYTO-09-17-0320-RVW.
